<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>test</title>
    <script>
        function f1() {

            // for(var i=0;i<10;i++)
            alert('hello');
        }
    </script>
    <style>
        .a{
            font-size: 20px;
            color: indigo;

        }



    </style>




</head>
<body>

<table class="a" width="50%" border="1" bgcolor="#7fff00">
    <tr>

        <th>hello</th>
        <th>hello</th>


    </tr>
    <tr>
        <th colspan="2">world</th>

    </tr>
    <tr>
        <th>world</th>

        <th rowspan="2">world</th>

    </tr>
    <tr>
        <th>world</th>




    </tr>


</table>









</body>
</html>